JP2017110177A - Polishing liquid, polishing liquid set and substrate polishing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing liquid which can improve the polishing rate of an SiOC (carbon-containing silicon oxide film).SOLUTION: A polishing liquid for SiOC polishing comprises an abrasive grain comprising cerium, a carboxylic acid compound in which the total of a carboxylic acid group and a carboxylate group is two, and water, and has a pH of 5.0 or more. The carboxylic acid compound preferably comprises at least one selected from the group consisting of adipic acid, 1,3-acetone dicarboxylic acid, α-ketoglutaric acid, iminodiacetic acid, thiomalic acid, diglycolic acid and salt thereof.SELECTED DRAWING: None

Description

  The present invention relates to a polishing liquid, a polishing liquid set, and a method for polishing a substrate.

  In the field of semiconductor manufacturing, along with the higher performance of VLSI devices, the conventional miniaturization technology on the extension line has reached the limit of achieving both higher integration and higher speed that can meet the above-mentioned higher performance. Yes. For this reason, a technology for multilayering wiring (high integration in the vertical direction) has also been developed while further miniaturizing semiconductor elements. One of the most important techniques in the process required for such multilayer wiring is a chemical mechanical polishing (chemical mechanical polishing, hereinafter referred to as “CMP”) technique. In multilayer wiring, it is essential to flatten devices one by one in order to ensure the depth of focus of lithography. This is because when the device has irregularities, it becomes difficult to focus in the exposure process or a fine wiring structure cannot be formed.

  Such CMP technology includes, for example, planarization of an interlayer insulating film, etc., and a plug after a silicon oxide film (film containing silicon oxide) is embedded in a metal wiring (for example, plugs of Al, Cu, Co, W, etc.) Planarization of an insulating film between metal wiring (organosilicate glass, carbon-containing silicon oxide film (SiOC film) such as MSQ; plasma oxide film such as BPSG, HDP-SiO, p-TEOS), or It is also applied to planarization of a plasma oxide film embedded after forming an element isolation structure, and has become an indispensable technique for semiconductor manufacturing.

Japanese Patent No. 4564735

  Incidentally, in recent years, in order to improve the performance of LSIs, it has been studied to use SiOC having a lower relative dielectric constant in a place where a plasma oxide film has been conventionally applied. However, when SiOC is polished using a conventional polishing liquid, a sufficient polishing rate tends not to be obtained. Therefore, it is required for the polishing liquid for such applications to improve the polishing rate of SiOC as compared with the conventional case.

  This invention is made | formed in view of the said subject, and it aims at providing the polishing liquid which can improve the grinding | polishing speed | rate of SiOC. Another object of the present invention is to provide a polishing liquid set for obtaining the polishing liquid. Another object of the present invention is to provide a method for polishing a substrate using the polishing liquid.

  The polishing liquid according to the present invention (SiOC polishing polishing liquid) is a carboxylic acid compound in which the total of cerium-containing abrasive grains, a carboxylic acid group (hereinafter also referred to as “carboxyl group”) and a carboxylic acid group is 2. And water, and the pH is 5.0 or more.

  According to the polishing liquid of the present invention, the polishing rate of SiOC can be improved.

  By the way, with the technique of the said patent document 1, it is trying to improve the grinding | polishing speed | rate of SiOC using polyether modified silicone. However, the technique of Patent Document 1 cannot obtain a sufficient polishing rate for SiOC. On the other hand, according to the polishing liquid according to the present invention, a sufficient polishing rate of SiOC can be obtained.

  The abrasive preferably contains at least one selected from the group consisting of cerium oxide and cerium hydroxide.

  The carboxylic acid compound preferably contains at least one selected from the group consisting of adipic acid, 1,3-acetone dicarboxylic acid, α-ketoglutaric acid, iminodiacetic acid, thiomalic acid, diglycolic acid, and salts thereof.

  The polishing liquid according to the present invention may further contain a pH adjuster.

  The polishing liquid according to the present invention may further contain a polymer compound having at least one selected from the group consisting of a carboxylic acid group and a carboxylic acid group. As a result, dishing of the SiOC film in the recesses (a phenomenon in which the recesses after the completion of polishing are recessed like a dish) can be reduced (see FIG. 1).

  The content of the polymer compound is preferably 0.001 to 2% by mass based on the total mass of the polishing liquid.

  One embodiment of the present invention relates to the use of the polishing liquid for polishing a surface to be polished containing SiOC. In other words, one embodiment of the polishing liquid according to the present invention is preferably used for polishing a surface to be polished containing SiOC.

  In the polishing liquid set according to the present invention, the constituents of the polishing liquid are stored separately in a first liquid and a second liquid, the first liquid contains the abrasive grains and water, and the second liquid The liquid contains the carboxylic acid compound and water. According to the polishing liquid set concerning the present invention, the same effect as the polishing liquid concerning the present invention can be acquired.

  The substrate polishing method according to the present invention may comprise a step of polishing a surface to be polished of the substrate using the polishing liquid. According to such a method for polishing a substrate, the same effects as those of the polishing liquid according to the present invention can be obtained.

  The substrate polishing method according to the present invention includes a step of polishing a surface to be polished of a substrate using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set. May be. According to such a method for polishing a substrate, the same effects as those of the polishing liquid according to the present invention can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the polishing liquid which can improve the grinding | polishing speed | rate of SiOC, a polishing liquid set, and the grinding | polishing method of a base | substrate can be provided. According to the present invention, SiOC can be removed by polishing. The present invention can be used for CMP of a semiconductor substrate. The present invention can be used to polish a surface to be polished containing SiOC.

  According to the present invention, use of a polishing liquid or a polishing liquid set for polishing SiOC can be provided. According to the present invention, use of a polishing liquid or a polishing liquid set for CMP of a semiconductor substrate can be provided. ADVANTAGE OF THE INVENTION According to this invention, use of the polishing liquid or polishing liquid set for grinding | polishing the to-be-polished surface containing SiOC can be provided.

It is the cross-sectional schematic of the grinding | polishing process in forming the STI structure of a semiconductor.

  Hereinafter, a polishing liquid, a polishing liquid set, and a substrate polishing method using the polishing liquid or the polishing liquid set according to an embodiment of the present invention will be described in detail.

<Definition>
In this specification, the term “process” is not limited to an independent process, and is included in the term if the intended action of the process is achieved even when it cannot be clearly distinguished from other processes. It is. The numerical range indicated by using “to” indicates a range including the numerical values described before and after “to” as the minimum value and the maximum value, respectively. The amount of each component in the composition means the total amount of the plurality of substances present in the composition unless there is a specific notice when there are a plurality of substances corresponding to each component in the composition. “Polishing rate” means the rate at which material is removed per unit time (removal rate = removal rate). “Polished material” means a material exposed on the surface to be polished. The “material to be polished” means a material that should be actively polished and removed at a high polishing rate. “A or B” only needs to include either A or B, and may include both. The numerical range “A or more” means A and a range exceeding A. The numerical range “A or less” means A and a range less than A.

<Polishing liquid>
The polishing liquid (SiOC polishing polishing liquid) according to this embodiment is a composition that touches the surface to be polished during polishing, and is, for example, a CMP polishing liquid. The polishing liquid according to the present embodiment contains abrasive grains containing cerium, a carboxylic acid compound having a total of 2 carboxylic acid groups and carboxylate groups, and water, and has a pH of 5.0 or more. The essential components and components that can be optionally added are described below.

(Abrasive grains)
In the present embodiment, the abrasive grains contain cerium from the viewpoint of obtaining a polishing action on SiOC. Constituents of abrasive grains containing cerium include cerium oxide (ceria), cerium hydroxide, ammonium cerium nitrate, cerium acetate, cerium sulfate hydrate, cerium bromate, cerium bromide, cerium chloride, cerium oxalate, nitric acid Examples include cerium, cerium carbonate, and cerium-modified products. Examples of the modified cerium include those obtained by modifying the surface of particles containing cerium oxide, cerium hydroxide and the like with an alkyl group, and composite particles in which other particles are attached to the surface of particles containing cerium. The abrasive grains preferably contain at least one selected from the group consisting of cerium oxide and cerium hydroxide, and more preferably contain cerium oxide, from the viewpoint of stabilizing the polishing rate of SiOC. As abrasive grains containing cerium, particles containing cerium oxide (hereinafter referred to as “cerium oxide particles”), particles containing cerium hydroxide (cerium hydroxide particles), and the like can be used.

  There is no restriction | limiting in particular as a cerium oxide particle, A well-known thing can be used. Among these, cerium oxide particles are preferably obtained by oxidizing cerium salts such as carbonates, nitrates, sulfates, and oxalates. Examples of the oxidation method include a baking method of baking the cerium salt at 600 to 900 ° C., a chemical oxidation method of oxidizing the cerium salt using an oxidizing agent such as hydrogen peroxide, and the like.

  In the case of using cerium oxide particles, the larger the crystallite diameter (crystallite diameter) of the cerium oxide particles and the smaller the crystal distortion (that is, the better the crystallinity), the faster the polishing is possible. There is a tendency that abrasive scratches are likely to enter the abrasive material. From the above viewpoint, preferable cerium oxide particles include particles composed of two or more crystallites and having a crystal grain boundary. Among these, particles having a crystallite diameter of 5 to 300 nm are more preferable. Another preferable cerium oxide particle includes colloidal ceria particles having a crystallite diameter of 5 to 300 nm (for example, colloidal ceria manufactured by Rhodia).

  The average particle diameter of the abrasive grains is preferably 10 nm or more, more preferably 20 nm or more, and still more preferably 50 nm or more, from the viewpoint of obtaining a better polishing rate for SiOC. The average particle size of the abrasive grains is preferably 500 nm or less, more preferably 400 nm or less, and still more preferably 300 nm or less, from the viewpoint that the material to be polished is less likely to be damaged. From these viewpoints, the average particle size of the abrasive grains is preferably 10 to 500 nm, more preferably 20 to 400 nm, and still more preferably 50 to 300 nm.

  Here, the average particle diameter of the abrasive grains was measured as a refractive index of 1.93 and an absorption of 0 using a laser diffraction particle size distribution meter Mastersizer Microplus (manufactured by Malvern, trade name (“Mastersizer” is a registered trademark)). It means the value of D50 (median diameter of volume distribution, cumulative median value) of the measurement sample to be measured. For the measurement of the average particle diameter, a sample having an appropriate content (for example, a content at which the measurement transmittance (H) with respect to a He—Ne laser is 60 to 70%) is used. In addition, when the polishing liquid containing abrasive grains is stored separately in a cerium slurry in which abrasive grains are dispersed in water and an additive liquid, the cerium slurry can be diluted to an appropriate content and measured. it can.

  In addition, an abrasive grain may contain components other than cerium. As a constituent component of such abrasive grains, for example, selected from the group consisting of silica, alumina, zirconia, manganese oxide, magnesium oxide, titania, germania, resin, diamond, silicon carbide, cubic boron nitride, and modified products thereof. At least one kind. An abrasive grain can be used individually by 1 type or in combination of 2 or more types. Colloidal alumina can also be used as the alumina. Examples of the modified product include silica, alumina, zirconia, titania, germania, manganese oxide, magnesium oxide, etc. whose surface is modified with an alkyl group, composite particles in which other particles are attached to the surface of one particle, etc. Is mentioned.

  The abrasive grains may be obtained by any manufacturing method. For example, oxide production methods include solid phase methods such as firing; liquid phase methods such as precipitation methods, sol-gel methods, and hydrothermal synthesis methods; gas phase methods such as sputtering methods, laser methods, and thermal plasma methods. Can be used.

  When the abrasive grains are aggregated, the aggregated abrasive grains may be mechanically pulverized. As the pulverization method, for example, a dry pulverization method using a jet mill or the like, and a wet pulverization method using a planetary bead mill or the like are preferable. For the jet mill, for example, a method described in “Chemical Engineering Journal”, Vol. 6, No. 5, (1980), pages 527 to 532 can be applied.

  When the abrasive grains are applied to the polishing liquid, it is preferable to obtain a slurry by dispersing the abrasive grains in water which is a main dispersion medium. Examples of the dispersion method include a method using a homogenizer, an ultrasonic disperser, a wet ball mill, and the like in addition to a dispersion treatment using a normal stirrer. Regarding the dispersion method and the particle size control method, for example, the method described in Chapter 3 “Latest Development Trends and Selection Criteria of Various Dispersers” in “Dispersion Technology Complete Collection” [Information Organization, July 2005] Can be used. Moreover, the dispersibility of an abrasive grain can also be improved by lowering the electrical conductivity of a dispersion containing abrasive grains (for example, 500 mS / m or less). As a method of lowering the electrical conductivity of the dispersion, solid-liquid separation is performed by centrifugation to separate the abrasive grains from the dispersion medium, the supernatant liquid (dispersion medium) is discarded, and a dispersion medium with low electrical conductivity is added. Examples of the method of redispersing include ultrafiltration, a method using an ion exchange resin, and the like.

  The abrasive grains dispersed by the above method may be further finely divided. Examples of the fine particle method include a sedimentation classification method (a method in which abrasive grains are centrifuged with a centrifuge and then forcedly settled, and only the supernatant liquid is taken out). In addition, a high-pressure homogenizer that causes the abrasive grains in the dispersion medium to collide with each other at a high pressure may be used.

  The content of abrasive grains containing cerium (for example, cerium oxide particles) is preferably 20% by mass or less, more preferably 10% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of easily suppressing aggregation of the abrasive grains. 5 mass% or less is further more preferable, 3 mass% or less is especially preferable, and 1 mass% or less is very preferable. The content of abrasive grains containing cerium (for example, cerium oxide particles) is preferably 0.01% by mass or more, based on the total mass of the polishing liquid, from the viewpoint that an effect of improving the polishing rate of SiOC is easily obtained. 1 mass% or more is more preferable, and 0.2 mass% or more is still more preferable. From these viewpoints, the content of the abrasive grains (for example, cerium oxide particles) is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, based on the total mass of the polishing liquid. 2-5 mass% is still more preferable.

  The content of the abrasive grains is preferably 20% by mass or less, more preferably 10% by mass or less, still more preferably 5% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of easily suppressing the aggregation of the abrasive grains. 3 mass% or less is especially preferable, and 1 mass% or less is very preferable. The content of the abrasive grains is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, based on the total mass of the polishing liquid, from the viewpoint that the effect of improving the polishing rate of SiOC is easily obtained. More preferably 2% by mass or more. From these viewpoints, the content of abrasive grains is preferably 0.01 to 20% by mass, more preferably 0.1 to 10% by mass, and 0.2 to 5% by mass based on the total mass of the polishing liquid. Further preferred.

(Additive)
The polishing liquid according to this embodiment contains an additive. Here, the “additive” means a polishing liquid other than abrasive grains and water in order to adjust polishing characteristics such as polishing speed and polishing selectivity; and polishing liquid characteristics such as abrasive dispersibility and storage stability. Refers to the substance contained.

  The polishing liquid according to this embodiment contains a carboxylic acid compound having a total of 2 carboxylic acid groups and carboxylic acid groups as an additive. By using the carboxylic acid compound, an effect of improving the polishing rate of SiOC can be obtained. Although the factors for obtaining such effects are not clear, for example, the following factors can be mentioned. That is, the carboxyl group acts on SiOC, and the surface of SiOC becomes hydrophilic. As a result, it is considered that the abrasive grains easily adhere to the SiOC and the polishing rate is improved.

  Examples of the carboxylic acid compound include adipic acid, aspartic acid, acetylenedicarboxylic acid, 1,3-acetone dicarboxylic acid, α-aminoadipic acid, 2-amino-3-carboxymuconic acid semialdehyde, 2-aminomuconic acid, and aldaric acid. , Α-ketoglutaric acid, isatoic acid, isophthalic acid, isopropylmalic acid, itaconic acid, iminodiacetic acid, oxaloacetic acid, quinolinic acid, glutaconic acid, glutamic acid, glutaric acid, succinic acid, chorismic acid, diaminopimelic acid, dipicolinic acid, oxalic acid , Tartaric acid, suberic acid, sebacic acid, tartronic acid, terephthalic acid, vamoic acid, malic acid, thiomalic acid, bicinchoninic acid, 2-hydroxy-3-oxosuccinic acid, pimelic acid, phthalic acid, 4-fumarylacetoacetic acid, 4-malelaceto Acetic acid, malonic acid, muco Acid, mesaconic acid, N-methyl-D-aspartic acid, and diglycolic acid; and salts thereof.

  From the viewpoint of further improving the effect of improving the polishing rate of SiOC, the carboxylic acid compound is composed of adipic acid, 1,3-acetone dicarboxylic acid, α-ketoglutaric acid, iminodiacetic acid, thiomalic acid, diglycolic acid and salts thereof. It is preferable to include at least one selected from the group consisting of, and more preferable to include at least one selected from the group consisting of α-ketoglutaric acid, diglycolic acid and salts thereof.

  In the polishing liquid according to this embodiment, the carboxylic acid compound can be used alone or in combination of two or more for the purpose of adjusting the polishing rate of SiOC.

  The lower limit of the content of the carboxylic acid compound is preferably 0.005% by mass or more and 0.01% by mass or more based on the total mass of the polishing liquid from the viewpoint of further improving the improvement effect of the polishing rate of SiOC. More preferred is 0.1% by mass or more. The upper limit of the content of the carboxylic acid compound is preferably 3.0% by mass or less, more preferably 1.0% by mass or less, based on the total mass of the polishing liquid, from the viewpoint of suitably maintaining storage stability. More preferably, it is 5 mass% or less. In addition, when using a some compound as said carboxylic acid compound, it is preferable that the sum total of content of each compound satisfy | fills the said range.

[Polymer Compound A]
The polishing liquid according to this embodiment may contain a polymer compound A (excluding the carboxylic acid compound) having at least one selected from the group consisting of a carboxylic acid group and a carboxylic acid group. The high molecular compound A can be used individually by 1 type or in combination of 2 or more types. As the polymer compound A, a polymer obtained by polymerizing a monomer containing at least one selected from the group consisting of acrylic acid and methacrylic acid or a salt thereof (hereinafter referred to as “(meth) acrylic acid polymer”). Are generally referred to as “)”. The said monomer may contain the other monomer (except acrylic acid and methacrylic acid) copolymerizable with acrylic acid or methacrylic acid. By using the polymer compound A, dishing due to SiOC overpolishing can be reduced.

  Examples of the other monomers (other monomers copolymerizable with acrylic acid or methacrylic acid) include, for example, crotonic acid, pentenoic acid, hexenoic acid, heptenoic acid, octenoic acid, nonenoic acid, decenoic acid, and undecene. Examples thereof include unsaturated carboxylic acids such as acid, dodecenoic acid, tridecenoic acid, tetradecenoic acid, pentadecenoic acid, hexadecenoic acid and heptadecenoic acid; vinyl compounds such as ethylene, propylene and styrene.

  The terminal of the polymer compound A preferably has a low molecular weight and is hydrophilic.

  Although the weight average molecular weight of the high molecular compound A does not have a restriction | limiting in particular, 100-150,000 are preferable and 1000-80000 are more preferable. When the weight average molecular weight of the polymer compound A is 100 or more, a good polishing rate tends to be easily obtained when a material to be polished such as silicon oxide such as SiOC is polished. When the weight average molecular weight of the polymer compound A is 150,000 or less, the storage stability of the polishing liquid tends to be difficult to decrease.

The weight average molecular weight of the polymer compound A can be measured by measuring under the following conditions and reading the value obtained as “Mw”.
{Measurement condition}
Equipment used (detector): Hitachi, Ltd., “L-3300” differential refractometer for liquid chromatograph Pump: Hitachi, Ltd., “L-7100” for liquid chromatograph
Degas equipment: None Data processing: GPC integrator “D-2520” manufactured by Hitachi, Ltd.
Column: “Shodex Asahipak GF-710HQ” manufactured by Showa Denko KK, inner diameter 7.6 mm × 300 mm
Eluent: 50 mM Na ₂ HPO ₄ aqueous solution / acetonitrile = 90/10 (v / v)
Measurement temperature: 25 ° C
Flow rate: 0.6 mL / min Measurement time: 30 minutes Sample: Adjust the concentration with a solution having the same composition as the eluent so that the resin concentration is 2% by mass, and filter through a 0.45 μm polytetrafluoroethylene filter. Prepared sample Injection volume: 0.4 μL
Reference material: Polymer Laboratories, narrow molecular weight sodium polyacrylate

  The content of the polymer compound A in the polishing liquid is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and still more preferably 0.1% by mass or more, based on the total mass of the polishing liquid. The content of the polymer compound A is preferably 2% by mass or less, more preferably 1% by mass or less, and still more preferably 0.5% by mass or less, based on the total mass of the polishing liquid. When the content of the polymer compound A is 0.001 to 2 mass%, the dishing amount, wiring density dependency, and the like can be reduced, and the surface flatness after polishing can be improved.

[Dispersant]
The polishing liquid according to the present embodiment can contain a dispersant (excluding the polymer compound A). The content of the dispersant is preferably 0.001 to 4% by mass based on the total mass of the abrasive grains. Examples of the dispersant include a water-soluble anionic dispersant, a water-soluble nonionic dispersant, a water-soluble cationic dispersant, and a water-soluble amphoteric dispersant. Among these, a water-soluble anionic dispersant or a water-soluble cationic dispersant is preferable from the viewpoint of high electrostatic repulsion and good dispersibility. The polymer compound A can also be used for dispersing the abrasive grains.

  When the polishing liquid according to the present embodiment contains a cationic polymer, abrasive grains containing cerium (such as cerium oxide particles) tend to have a positive charge. In this case, the polishing rate of silicon nitride (SiN) or the like can be suppressed. Examples of cationic polymers include homopolymers and copolymers of diallyldialkylammonium salts, homopolymers and copolymers of diallylalkylamine salts, polyallylamines such as homopolymers and copolymers of diallylamine salts, and the like. It is done.

  Specifically, diallyldialkylammonium salts include, for example, diallyldimethylammonium chloride, diallyldimethylammonium bromide, diallyldimethylammonium iodide, diallyldimethylammonium methyl sulfate, diallyldimethylammonium ethyl sulfate, diallylethylmethylammonium chloride, diallylethyl Methyl ammonium bromide, diallyl ethyl methyl ammonium iodide, diallyl ethyl methyl ammonium methyl sulfate, diallyl ethyl methyl ammonium ethyl sulfate, diallyl diethyl ammonium chloride, diallyl diethyl ammonium bromide, diallyl diethyl ammonium iodide, diallyl diethyl ammonium methyl sulfate , Diallyl diethyl ammonium ethyl sulfate, diallyl methyl-propyl ammonium chloride, diallyl methyl-propyl ammonium bromide, diallyl methyl-propyl ammonium iodide, diallyl methyl-propyl ammonium methyl sulfate, and, may be mentioned diallyl methylpropyl ammonium ethylsulfate.

  Examples of diallylalkylamine salts include diallylmethylamine hydrochloride, diallylmethylamine hydrobromide, diallylmethylamine hydroiodide, diallylmethylamine sulfate, diallylmethylamine methanesulfonate, diallylethylamine hydrochloride Salt, diallylethylamine hydrobromide, diallylethylamine hydroiodide, diallylethylamine sulfate, diallylethylamine methanesulfonate, diallylpropylamine hydrochloride, diallylpropylamine hydrobromide, diallylpropylamine iodide Mention may be made of hydrogenates, diallylpropylamine sulfate and diallylpropylamine methanesulfonate.

  Examples of diallylamine salts include diallylamine hydrochloride, diallylamine hydrobromide, diallylamine hydroiodide, diallylamine sulfate, and diallylamine methanesulfonate.

[PH adjuster]
The polishing liquid may contain a pH adjuster. However, if the polishing liquid is in the predetermined pH range even if it does not contain a pH adjuster, the pH adjuster need not be added.

  There is no restriction | limiting in particular as a pH adjuster, An inorganic acid, an organic acid, an organic base, an inorganic base, etc. are mentioned. Examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, boric acid and the like. Examples of the inorganic base include ammonia. A buffer may be added to stabilize the pH. Examples of such a buffer include an acetate buffer. Each of the pH adjusting agent and the buffer can be used alone or in combination of two or more.

[Other additives]
The polishing liquid according to this embodiment may further contain other additives for the purpose of adjusting polishing characteristics such as polishing rate; and characteristics such as dispersibility of abrasive grains. Other additives can be used alone or in combination of two or more.

  Examples of other dispersants include water-soluble polymers used for adjusting polishing properties such as flatness and in-plane uniformity. Moreover, polishing liquid may contain solvents other than water (for example, polar solvents, such as ethanol, acetic acid, acetone, etc.) as an additive as needed.

  Examples of the water-soluble polymer include polysaccharides such as alginic acid, pectic acid, carboxymethylcellulose, agar, curdlan and guar gum, and vinyl polymers such as polyvinyl alcohol and polyacrolein. Here, the “water-soluble polymer” is defined as a polymer that dissolves 0.1 g or more in 100 g of water at 25 ° C.

  When using a water-soluble polymer, the lower limit of the content of the water-soluble polymer is based on the total mass of the polishing liquid from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of abrasive grains. 0.0001 mass% or more is preferable, 0.001 mass% or more is more preferable, and 0.01 mass% or more is still more preferable. The upper limit of the content of the water-soluble polymer is preferably 5% by mass or less, preferably 1% by mass based on the total mass of the polishing liquid, from the viewpoint of obtaining the effect of adding the water-soluble polymer while suppressing sedimentation of the abrasive grains. % Or less is more preferable, and 0.5 mass% or less is still more preferable. When using a some compound as water-soluble polymer, it is preferable that the sum total of content of each compound satisfy | fills the said range.

  When other additives are used, the content of each other additive is 0 on the basis of the total mass of the polishing liquid from the viewpoint of obtaining the effect of addition of other additives while suppressing sedimentation of abrasive grains. 0.001 to 10% by mass is preferable. When using a some compound as another additive, it is preferable that the sum total of content of each compound satisfy | fills the said range.

(water)
The water that is the medium of the polishing liquid is not particularly limited, but deionized water, ion exchange water, ultrapure water, and the like are preferable.

(PH of polishing liquid)
The pH of the polishing liquid according to this embodiment is 5.0 or more from the viewpoint of obtaining the effect of improving the polishing rate of SiOC. The pH of the polishing liquid according to this embodiment is preferably 5.5 or more, and more preferably 6.0 or more, from the viewpoint of easily obtaining the effect of improving the polishing rate of SiOC. The pH of the polishing liquid according to this embodiment is preferably 12 or less, more preferably 11 or less, still more preferably 10 or less, and particularly preferably 9.5 or less from the viewpoint of safety. The pH is defined as the pH at a liquid temperature of 25 ° C.

  The pH of the polishing liquid according to this embodiment can be measured with a pH meter (for example, model number PHL-40 manufactured by Electrochemical Instruments Co., Ltd.). Specifically, for example, phthalate pH buffer (pH 4.01), neutral phosphate pH buffer (pH 6.86) and borate pH buffer (pH 9.18) are used as standard buffers. After calibrating the pH meter at three points, the electrode of the pH meter is put into the polishing liquid, and the value after 2 minutes has passed and stabilized is measured. At this time, both the standard buffer solution and the polishing solution are set to 25 ° C.

(Type of polishing liquid)
The polishing liquid according to this embodiment may be stored as a one-part polishing liquid containing at least abrasive grains, the carboxylic acid compound, and water, and includes a slurry (first liquid) and an additive liquid (second liquid). May be stored as a two-pack type polishing liquid set (for example, a polishing liquid set for CMP) in which the constituents of the polishing liquid are divided into a slurry and an additive liquid so as to be the polishing liquid. The slurry includes at least abrasive grains and water, for example. The additive liquid contains at least the carboxylic acid compound and water, for example. It is preferable that the carboxylic acid compound and other additives are contained in the additive liquid among the slurry and the additive liquid. However, the additive having the effect of improving the dispersibility of the abrasive grains is preferably contained in the slurry of the slurry and the additive liquid. For example, in the polishing liquid set, the constituents of the polishing liquid are stored separately in a slurry (first liquid) and an additive liquid (second liquid), and the slurry contains abrasive grains and water, and the additive liquid The aspect which contains the said carboxylic acid compound and water may be sufficient. The constituents of the polishing liquid may be stored as a polishing liquid set divided into three or more liquids.

  In the polishing liquid set, slurry and additive liquid are mixed immediately before polishing or at the time of polishing to prepare a polishing liquid. Further, the one-part polishing liquid is stored as a stock liquid for polishing liquid with a reduced water content, and may be used by diluting with water immediately before polishing or at the time of polishing. The two-pack type polishing liquid set may be stored as a slurry storage liquid and an additive liquid storage liquid with a reduced water content, and may be diluted with water immediately before polishing or at the time of polishing.

  In the case of a one-pack type polishing liquid, as a method of supplying the polishing liquid onto the polishing surface plate, a method of directly supplying the polishing liquid and supplying it; a storage liquid for polishing liquid and water are supplied through separate pipes; A method in which these are combined and mixed and supplied; a method in which a stock solution for polishing liquid and water are mixed and supplied in advance can be used.

  When storing as a two-pack type polishing liquid set divided into slurry and additive liquid, the polishing rate can be adjusted by arbitrarily changing the blend of these two liquids. In the case of polishing using a polishing liquid set, there are the following methods for supplying the polishing liquid onto the polishing surface plate. For example, the slurry and the additive liquid are sent through separate pipes, and these pipes are combined, mixed and supplied; the slurry storage liquid, the additive liquid storage liquid and water are sent through separate pipes, A method in which these are combined and mixed and supplied; a method in which slurry and additive solution are mixed and supplied in advance; and a method in which slurry storage solution, additive solution storage solution and water are mixed in advance and supplied it can. Further, it is possible to use a method of supplying the slurry and the additive liquid in the polishing liquid set onto the polishing surface plate, respectively. In this case, the surface to be polished is polished using a polishing liquid obtained by mixing the slurry and the additive liquid on the polishing surface plate.

<Manufacturing method of polishing liquid>
The method for producing a polishing liquid according to this embodiment is a method for producing a polishing liquid for removing at least a part of SiOC by CMP. The manufacturing method of the polishing liquid according to the present embodiment includes a polishing liquid manufacturing step of obtaining a polishing liquid by mixing at least abrasive grains, a carboxylic acid compound, and water. In the polishing liquid production process, each component may be mixed simultaneously, or each component may be mixed sequentially. The manufacturing method of the polishing liquid according to the present embodiment may include a step of obtaining abrasive grains containing cerium before the polishing liquid manufacturing step.

  The method for producing a polishing liquid according to this embodiment preferably includes a dispersion step of dispersing abrasive grains in water. A dispersion | distribution process is a process of mixing an abrasive grain and a dispersing agent, for example. In this case, the dispersant is preferably added in a step of obtaining a cerium slurry (cerium oxide slurry or the like). That is, it is preferable that the cerium slurry contains a dispersant. In the dispersion step, for example, abrasive grains, a dispersant, and water are mixed, and the abrasive grains are dispersed in water to obtain a cerium slurry.

<Polishing method of substrate>
The polishing method according to the present embodiment includes a step of polishing a surface to be polished containing SiOC using a polishing liquid. The substrate polishing method according to the present embodiment may include a polishing step of polishing the surface to be polished of the substrate using the one-component polishing liquid, and the slurry and the additive liquid in the polishing liquid set are mixed. A polishing step of polishing the surface to be polished of the substrate using the polishing liquid obtained in this manner may be provided. Further, the substrate polishing method according to the present embodiment may be a method for polishing a substrate having a single or a plurality of materials to be polished. For example, the one-component polishing liquid or the slurry in the polishing liquid set You may provide the grinding | polishing process of selectively grind | polishing SiOC with respect to a stopper material using the polishing liquid obtained by mixing an additive liquid. In this case, the base body may have, for example, a member containing SiOC and a member (stopper) containing a stopper material. As the stopper material, materials such as silicon nitride and polysilicon are preferable, and silicon nitride is more preferable.

  In the polishing step, for example, the polishing liquid is supplied between the polishing target material and the polishing pad in a state where the polishing target material of the substrate having the polishing target material is pressed against the polishing pad (polishing cloth) of the polishing surface plate. The material to be polished is polished by relatively moving the substrate and the polishing surface plate. In the polishing step, for example, at least a part of the material to be polished is removed by polishing.

  FIG. 1 is a schematic cross-sectional view of a polishing process in forming a semiconductor STI structure. The substrate polishing method according to the present embodiment will be further described with reference to FIG. First, as shown in FIG. 1 (A), a wafer (silicon substrate or the like) 1 having concave and convex portions (trench portions) and convex portions (active portions) formed on the surface, and a convex portion of the wafer 1 A base 100 having a silicon nitride film (SiN film) 2 formed on the surface of the wafer 1 and a SiOC film 3 formed so as to fill the irregularities on the surface of the wafer 1 is prepared.

  Next, the SiOC film 3 is polished using the polishing liquid, and the polishing is stopped when the SiOC film 3 on the convex portion is completely removed and the silicon nitride film 2 is exposed, whereby FIG. A substrate 200 shown in FIG. In the substrate 200 after polishing, it is preferable to reduce dishing of the SiOC film 3 in the recess. Specifically, the dishing amount 6 that is a value obtained by subtracting the thickness 5 of the SiOC film 3 in the recess from the depth 4 of the recess is preferably small.

  Examples of the substrate to be polished include a substrate. For example, a material to be polished is formed on a substrate for manufacturing a semiconductor element (for example, a semiconductor substrate on which an STI pattern, a gate pattern, a wiring pattern, etc. are formed). A substrate is mentioned. The substrate may be a substrate having one or more kinds as a material to be polished, or may be a substrate having one or more kinds of materials to be polished and one or more kinds of stopper materials. Good. Examples of the material to be polished include insulating materials such as SiOC (carbon-containing silicon oxide, organosilicate glass, MSQ, etc.), silicon oxide (excluding SiOC), and the like. Examples of the stopper material include silicon nitride and polysilicon. The material to be polished may be in the form of a film (film to be polished). The material to be polished and the stopper material may be in the form of a film (polishing target film and stopper film).

  By polishing the material to be polished (such as SiOC) formed on such a substrate with the polishing liquid and removing an excess portion, unevenness on the surface of the material to be polished is eliminated, and the entire surface of the material to be polished is removed. A smooth surface can be obtained. The polishing liquid according to this embodiment is preferably used for polishing a surface to be polished containing SiOC.

  Hereinafter, the polishing method according to this embodiment will be further described by taking a semiconductor substrate polishing method as an example. In the polishing method according to the present embodiment, as a polishing apparatus, a general polishing apparatus having a holder capable of holding a substrate such as a semiconductor substrate having a surface to be polished and a polishing surface plate to which a polishing pad can be attached. Can be used. For example, a motor or the like whose rotation speed can be changed is attached to each of the holder and the polishing surface plate. Examples of the polishing apparatus include a polishing apparatus manufactured by APPLIED MATERIALS (trade names: Mira-3400, Reflexion LK), and a polishing apparatus manufactured by Ebara Corporation (trade name: F-REX300).

  As the polishing pad, a general nonwoven fabric, foam, non-foam, or the like can be used. The material of the polishing pad is polyurethane, acrylic resin, polyester, acrylic-ester copolymer, polytetrafluoroethylene, polypropylene, polyethylene, poly-4-methylpentene, cellulose, cellulose ester, polyamide (for example, nylon (trade name)) And aramid), polyimide, polyimide amide, polysiloxane copolymer, oxirane compound, phenol resin, polystyrene, polycarbonate, epoxy resin and the like. As the material of the polishing pad, foamed polyurethane and non-foamed polyurethane are particularly preferable from the viewpoint of obtaining a further excellent polishing rate and flatness. The polishing pad may be grooved so that the polishing liquid accumulates.

Although there is no limitation on the polishing conditions, the rotation speed of the polishing platen is preferably 200 min ⁻¹ (rpm) or less so that the semiconductor substrate does not pop out, and the polishing pressure (processing load) applied to the semiconductor substrate causes polishing scratches. From the viewpoint of sufficiently suppressing this, 100 kPa or less is preferable. During polishing, it is preferable to continuously supply the polishing liquid to the polishing pad with a pump or the like. Although there is no restriction | limiting in this supply amount, it is preferable that the surface of a polishing pad is always covered with polishing liquid.

  The semiconductor substrate after polishing is preferably washed thoroughly under running water to remove particles adhering to the substrate. For cleaning, dilute hydrofluoric acid or ammonia water may be used in addition to pure water, and a brush may be used to improve cleaning efficiency. Further, after cleaning, it is preferable to dry the semiconductor substrate after water droplets adhering to the semiconductor substrate are removed using a spin dryer or the like.

  As a substrate to be polished in the polishing method according to the present embodiment, for example, individual semiconductors such as diodes, transistors, compound semiconductors, thermistors, varistors, thyristors; DRAM (dynamic random access memory), SRAM (static random)・ Access memory), EPROM (erasable programmable read only memory), mask ROM (mask read only memory), EEPROM (electrically erasable programmable read only memory), flash memory, etc. Memory elements; theoretical circuit elements such as microprocessors, DSPs and ASICs; integrated circuit elements such as compound semiconductors represented by MMICs (monolithic microwave integrated circuits); hybrid integration Road (Hybrid IC), light emitting diodes, can be applied to a substrate having such a photoelectric conversion element such as a charge coupled device.

  The polishing liquid according to the present embodiment is not limited to the polishing of SiOC, silicon nitride or the like formed on a semiconductor substrate as described in the above-described embodiment, but silicon oxide formed on a wiring board having a predetermined wiring, It can be applied to polishing an inorganic insulating material such as glass or silicon nitride; a material mainly containing polysilicon, Al, Cu, Ti, TiN, W, Ta, TaN or the like.

  As an electronic component including a substrate polished by the polishing method according to the present embodiment, various types can be cited. Electronic components include not only semiconductor elements but also optical glasses such as photomasks, lenses and prisms; inorganic conductive films such as ITO; optical integrated circuits composed of glass and crystalline materials; optical switching elements; optical waveguides; An optical single crystal such as a scintillator; a solid laser single crystal; a sapphire substrate for a blue laser LED; a semiconductor single crystal such as SiC, GaP, or GaAs; a glass substrate for a magnetic disk; a magnetic head. In these electronic components, by polishing each layer with the polishing liquid according to the present embodiment, high integration can be achieved and excellent characteristics can be exhibited.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in more detail, this invention is not limited to these Examples, unless it deviates from the technical idea of this invention. For example, the material of the polishing liquid and the blending ratio thereof may be materials and blending ratios other than the materials and blending ratios described in the present embodiment, and the composition and structure of the polishing object may be other than the compositions and structures described in the present embodiment. And the structure may be acceptable.

<Preparation of cerium oxide powder>
40 kg of commercially available cerium carbonate hydrate was placed in an alumina container and baked in air at 830 ° C. for 2 hours to obtain 20 kg of yellowish white powder. When the phase of this powder was identified by the X-ray diffraction method, it was confirmed to be cerium oxide. 20 kg of the obtained cerium oxide powder was dry-ground using a jet mill to obtain a cerium oxide powder containing cerium oxide particles.

<Preparation of polishing liquid for CMP>
Example 1
After mixing 200.0 g of the cerium oxide powder prepared above and 795.0 g of deionized water, 5 g of an aqueous ammonium polyacrylate solution (weight average molecular weight: 8000, 40 mass%) was added. Ultrasonic dispersion was performed with stirring to obtain a cerium oxide dispersion. Ultrasonic dispersion was performed at an ultrasonic frequency of 400 kHz and a dispersion time of 20 minutes.

  Thereafter, 1 kg of cerium oxide dispersion was placed in a 1 L container (height: 170 mm) and allowed to stand, and sedimentation classification was performed. After 15 hours of classification, the supernatant above a depth of 130 mm from the water surface was pumped up. The obtained supernatant cerium oxide dispersion was diluted with deionized water so that the solid content was 5% by mass to obtain an aqueous dispersion (slurry) containing cerium oxide particles.

  In order to measure the average particle diameter (D50) of the cerium oxide particles in the aqueous dispersion containing the cerium oxide particles, the dispersion is adjusted so that the transmittance (H) at the time of measurement with respect to the He—Ne laser is 60 to 70%. Diluted to obtain a measurement sample. Using a laser diffraction particle size distribution meter Mastersizer Microplus (Malvern, trade name ("Mastersizer" is a registered trademark)), the refractive index is 1.93, the absorption is 0, and the D50 of the measurement sample is measured. Was 150 nm.

  After mixing these in the same container in the order of water, dicarboxylic acid in Table 1 (A1, α-ketoglutaric acid, manufactured by Tokyo Chemical Industry Co., Ltd.), pH adjuster, and aqueous dispersion containing the cerium oxide particles. Then, a polishing slurry for CMP containing 1.0% by mass of cerium oxide particles and 0.10% by mass of dicarboxylic acid was prepared. “%” In Tables 1 to 3 represents “mass%” and represents the content based on the total mass of the polishing liquid.

(Examples 2 to 10 and Comparative Examples 1 to 3)
By mixing in the same procedure as in Example 1, CMP polishing liquids shown in Tables 1 to 3 were prepared. As additives, 1,3-acetone dicarboxylic acid (A2, manufactured by Tokyo Chemical Industry Co., Ltd.), diglycolic acid (A3, manufactured by Tokyo Chemical Industry Co., Ltd.), adipic acid (A4, manufactured by Tokyo Chemical Industry Co., Ltd.), Thiomalic acid (A5, manufactured by Tokyo Chemical Industry Co., Ltd.) and acetic acid (A6, manufactured by Wako Pure Chemical Industries, Ltd., reagent grade) were used. In Example 6, a polishing liquid containing dicarboxylic acid and polyacrylic acid (total number of carboxylic acid groups and carboxylic acid groups: more than 2) was prepared. In Examples 7 to 10, polishing liquids containing dicarboxylic acid and polymethacrylic acid (total number of carboxylic acid groups and carboxylic acid groups: more than 2) were prepared. In Comparative Example 1, a polishing liquid containing no additive was prepared. In Comparative Example 2, a polishing liquid containing no dicarboxylic acid and containing polymethacrylic acid (total number of carboxylic acid groups and carboxylic acid groups: more than 2) was prepared.

  The pH of the polishing slurry for CMP was measured with a pH meter (Model No. PHL-40 manufactured by Electrochemical Instrument Co., Ltd.). Three pH meters using phthalate pH buffer (pH 4.01), neutral phosphate pH buffer (pH 6.86) and borate pH buffer (pH 9.18) as standard buffers After calibration, the pH meter electrode was placed in the polishing liquid, and the value after 2 minutes had passed and stabilized was measured. The measurement results are shown in Tables 1 to 3.

<Polishing evaluation>
As a test wafer for CMP evaluation, a blanket substrate (Blanket wafer) on which no pattern was formed was used. As the blanket substrate, a substrate having a SiOC film (manufactured by Merck) on a silicon (Si) substrate (diameter: 300 mm) was used.

  A polishing apparatus (manufactured by APPLIED MATERIALS, product name: Reflexion LK) was used for polishing the test wafer for CMP evaluation. A test wafer for CMP evaluation was set in a holder to which a suction pad for attaching a substrate was attached. A polishing pad made of porous urethane resin (manufactured by Rohm and Haas Japan Co., Ltd., model number IC1010) was attached to a polishing surface plate having a diameter of 600 mm of the polishing apparatus. The holder was placed on a polishing platen with the surface on which the SiOC film as the film to be polished was placed facing down, and the processing load was set to 3.0 psi (20.6 kPa).

While the CMP polishing liquid to the polishing platen was added dropwise at a rate of 300 mL / min, the polishing plate and the CMP evaluation test wafer respectively ^93min -1, rotated at 87min ^-1, test CMP Rating The wafer was polished. Polishing was performed for 60 seconds. The polished wafer was thoroughly washed with pure water using a PVA brush (polyvinyl alcohol brush) and then dried.

  The film thickness of the film to be polished before and after polishing is measured using an optical interference type film thickness measuring device manufactured by Filmetrics Co., Ltd. (device name: F80), and the polishing rate on the blanket wafer is calculated from the average value of the film thickness change amount. did. The unit of the polishing rate is nm / min. The evaluation results are shown in Tables 1 to 3.

The symbols in the above table are as follows.
A1: α-ketoglutaric acid A2: 1,3-acetone dicarboxylic acid A3: Diglycolic acid A4: Adipic acid A5: Thiomalic acid A6: Acetic acid

  From the results of Tables 1 to 3, Examples 1 to 10 showed higher SiOC film polishing rates than the comparative examples.

  DESCRIPTION OF SYMBOLS 1 ... Wafer, 2 ... Silicon nitride film, 3 ... SiOC film, 4 ... Depth of recessed part, 5 ... Thickness of SiOC film in recessed part after grinding | polishing, 6 ... Dishing amount, 100,200 ... Base | substrate.

Claims (10)

Containing abrasive grains containing cerium, a carboxylic acid compound having a total of 2 carboxylic acid groups and carboxylic acid groups, and water,
A polishing liquid for polishing SiOC having a pH of 5.0 or more.   The polishing liquid according to claim 1, wherein the abrasive grains include at least one selected from the group consisting of cerium oxide and cerium hydroxide.   The carboxylic acid compound includes at least one selected from the group consisting of adipic acid, 1,3-acetone dicarboxylic acid, α-ketoglutaric acid, iminodiacetic acid, thiomalic acid, diglycolic acid and salts thereof. 2. The polishing liquid according to 2.   The polishing liquid according to any one of claims 1 to 3, further comprising a pH adjuster.   The polishing liquid according to any one of claims 1 to 4, further comprising a polymer compound having at least one selected from the group consisting of a carboxylic acid group and a carboxylic acid group.   The polishing liquid according to claim 5, wherein the content of the polymer compound is 0.001 to 2 mass% based on the total mass of the polishing liquid.   The polishing liquid according to claim 1, which is used for polishing a surface to be polished containing SiOC.   The constituents of the polishing liquid according to any one of claims 1 to 7 are stored separately in a first liquid and a second liquid, and the first liquid contains the abrasive grains and water, A polishing liquid set, wherein the second liquid contains the carboxylic acid compound and water.   A method for polishing a substrate, comprising a step of polishing a surface to be polished of the substrate using the polishing liquid according to claim 1.   A method for polishing a substrate, comprising a step of polishing a surface to be polished of a substrate using a polishing liquid obtained by mixing the first liquid and the second liquid in the polishing liquid set according to claim 8.

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